The primary objective of this study is to evaluate the variability of HIV RNA measurements using the CHIRON QUANTIPLEX HIV-1 RNA Assay over a 24 hour period in individuals with clinically stable HIV infection. The specific aims are: to estimate the within-day component of variance in viral RNA in clinically stable HIV-infected patients. To determine whether there is a diurnal pattern in HIV RNA levels. To establish criteria to measure a clinically meaningful change in response to therapy in viral RNA levels based on the degree of variance observed in serial measurements over a two day period in the absence of therapy.